The present invention is directed to a time division transmission system for an asychronous pulse train having means for converting the pulse repetition rate (PRR) of the pulse train to a higher PRR by the insertion of stuff pulses. This, for example, allows a 50 kilobit per second asychronous pulse train to be synchronized with a standard 64 kilobit per second frequency of a standard time divided transmission facility such as the Bell Telephone System's T1 carrier system.
One technique for converting a 50 kilobit per second (KBS) data stream incoming over a user's line to a standard 64 kilobit per second data steam is shown in U.S. Pat. No. 3,136,861 in the name of J. S. Mayo and assigned to Bell Telephone Laboratories. This patent discloses a stuffing system and a predictive technique which is employed to remove inserted signals even in the presence of large transmission error rates. However, there is still a need for a relatively simple system which maintains synchronization and at the same time is highly resistant to errors in order not to create an out-of-frame condition all of the foregoing being done with a fairly simple coding concept.